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Sputter cathode assembly and sputter coating device

Sputter cathode assembly and sputter coating device description/claims

This application claims priority to U.S. Provisional Patent Application No. 60/896,140, entitled “Sputter Cathode Assembly and Sputter Coating Device,” filed Mar. 21, 2007 which is incorporated by reference herein for all purposes.

This application also claims the benefit of European Patent Application No. EP 07104546.2, entitled “Sputter Cathode Assembly and Sputter Coating Device,” filed Mar. 21, 2007 which is incorporated by reference herein for all purposes.

The present invention relates to a sputter cathode assembly, particularly to a magnetron sputter cathode assembly, comprising at least one bearing system for rotatably supporting a rotatable cathode or target structure. Furthermore, the invention relates to a sputter coating device.

Sputtering is commonly used as a coating technology for coating substrates, e.g. large area glass substrates, within a vacuum chamber. In this sputtering process, plasma is generated within an enclosed reaction chamber for depositing a thin film of target material on a stationary substrate or on a substrate that moves through the chamber and passes the target.

In order to increase the sputtering rate, magnetron sputtering has been developed which involves configuring an external magnet field to trap electrons in a region above the surface of the target/cathode. Thus an increased particle density may be generated. Furthermore, particles are sputtered from a substantially cylindrical rotatable target to improve the material usage of the target. Rotatable target tubes are available in different diameters and in a wide range of materials.

In large substrate coating devices, long and heavy cathodes have to be provided. In order to support these cathodes, various support constructions have been proposed, e.g. in European Patent EP No: 1 355 343 A2 or U.S. Pat. No. 5,096,562. Cantilever type supports as well as two-end type supports are known. The entire disclosure of the foregoing references is incorporated herein by reference for all purposes.

In order to facilitate the rotation of the cathode or target, the cathode or target is supported by bearings. Usually a considerable number of bearings are arranged along the drive spindle extending from one or both sides of the cathode in order to provide sufficient and reliable support and positioning of the cathode. For example, at least two bearings are required to support the drive shaft and the cathode or target and to provide sufficient stability for the drive shaft in the radial direction and in the axial direction. However, most of the known constructions require considerable constructed space in order to fulfill the security, precision and reliability needs.

The bearings include journal and thrust bearings to support the drive shaft. For example, it is known to use single-ball bearings or double-ball bearings including an outer race, an inner race and one or two sets of balls positioned between the inner race and the outer race. The balls are circumferentially spaced relative to one another by a cage.

Above all, in most applications it is required to deposit a sufficiently homogeneous and uniform layer of coating material over the complete substrate surface. This may, however, be particularly critical in marginal areas of the surface of the substrate surface. Therefore, attempts have been made to increase the thickness of the target material at both ends of the target. Furthermore, targets having an excess length projecting over the edge of the substrate are provided.

As described above, conventional support constructions are quite complicated and require a lot of installation space, particularly in the longitudinal direction of the cathode.

It is an object of the present invention to provide a sputter cathode assembly and a sputter coating device having a rotatable cathode requiring reduced installation space, but without affecting precision and stability requirements. This object is achieved by providing a sputter cathode assembly and a sputter coating device having features that are subject matter described in details herein.

According to the invention, a sputter cathode assembly, particularly a magnetron sputter cathode assembly, comprises at least one bearing system for rotatably supporting a rotatable cathode or target structure. The bearing system comprises at least one combined axial and radial bearing.

The sputter cathode assembly is provided for a rotary cathode device having a rotary cathode or target structure, particularly a substantially cylindrical cathode or target.

The sputter cathode assembly comprises a particular bearing system which is arranged between a stationary housing or fixed member and the rotatable cathode or target. The fixed member may be attached to the wall of a coating chamber.

The combined axial and radial bearing is a single bearing combining an axial bearing (i.e. thrust bearing) to withstand thrust and a radial bearing (i.e. journal bearing) to withstand radial forces. The “combined” axial and radial bearing usually comprises one outer race component, one inner race component and a set of rollers, e.g. cylinders, arranged in a retainer structure. The rollers may be held in an annular cage arranged between the outer race and the inner race.

In conventional support units for magnetrons, at least two bearings spaced along the rotation axis are provided for rotatably supporting the magnetron. Because of the installation of just one bearing instead of two or more bearings the construction may be small and compact. Thus the required installation space may be reduced. Furthermore, the inventor has found out that the stability and precision of a combined axial and radial bearing in a sputter coating device are even better than the stability and precision of two or more axially spaced thrust and/or journal bearings.

When arranging compact support units according to the invention within a coating chamber, the axial length of the target could be increased because of the shorter length of the support units. Therefore, the excess length of the target exceeding the width of the substrate may be increased to result in an improved uniformity of the coating in the marginal areas of the substrate surface.

Particularly, the combined axial and radial bearing is a cross roller bearing. In the cross roller bearing, the substantially elongated cylindrical rollers are crossed at a suitable angle, for example, at a 90° angle, in an alternating fashion and enclosed between an inner race and an outer race.

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